Building The Ultimate 750 Holley 3310Pumping up the popular carb a la Proform
Over the past 25 years, Holley has probably sold millions of 750 cfm vacuum secondary (#3310) carburetors. I know because I've personally purchased more than twenty 3310s for various cars over the past 25 years and written thousands of car features on vehicles equipped with the ol' standby. It's without a doubt the most universal carb ever built for the performance aftermarket. The same is true for Holley's 650 cfm (#4777) and 750 cfm (#4779) double pumpers. It's hard to find an application where they won't perform well.
Times are changing fast-and while electronic fuel injection is gaining in popularity, the venerable Holley carburetor is moving forward too. A couple of years ago Holley released its HP Series of double pumpers. The HP Series is Holley's answer to the carb tuners out there who were charging exorbitant sums of money to modify existing Holley carbs for more flow and performance. The HP Series of carbs featured deleted choke housings, radiused airhorn inlet surfaces, advanced boosters and more. Specialty carb makers such as Barry Grant introduced advanced carb designs such as its Demon series. Now you can purchase a fully prepped carb for virtually any application.
Left in the dust is the old Holley 3310 and the early double pumpers. These carbs are relatively cheap in rebuildable condition at local swap meets, or you just might have a working version on your current performance car. The folks at Proform in Roseville, Michigan had a great idea. Why not offer affordable replacement carburetor bodies that have most of the improvements found in high-dollar contemporary performance carburetors?
So what they've done is offer Holley main body replacements for 3310s and 650-750 cfm double pumpers. The replacements feature removed choke shrouds, symmetrical venturii spacing, contoured and blended airhorn inlet surfaces, down-leg boosters and screw-in high speed and idle air bleeds. You simply replace the center section of your carburetor in less time than it takes to rebuild the carb, and you have a new carburetor capable of increased airflow, higher venturii velocity for better response and improved tunability. What you no longer have is a choke, an important consideration for those enthusiasts who operate their vehicles in cold weather.
Proform's carburetor main body replacements come complete with everything you need to convert your current Holley carb. The main body assembly is precision die cast and is zinc-dichromate plated to match the Holley metering blocks and float bowls. It comes complete with screw-in, high-speed and idle air bleeds in place, throttle body-to-main body gasket, non-stick metering block and fuel bowl gaskets and nylon fuel bowl screw gaskets. A donor Holley carb contributes its throttle body, metering blocks, float bowl assemblies and vacuum diaphram (if applicable). Detailed step-by-step installation instructions are available on Proform's web site at www.proformparts.com.
Tests have shown airflow improvements of up to 130 cfm, and horsepower increases of 25 to 50 horsepower. This is a great power-per-dollar value when you consider the reasonable price of $159-$199 (depending on where you shop). Additional parts for fine tuning such as screw-in airbleeds, jets and secondary diaphram springs are available from Quick Fuel Technologies, 2352 Russellville Road, Bowling Green, KY 42101. Phone 270 793-0900.
autoMedia.com was looking for a large (900 cfm) vacuum secondary carb for a street-driven big-block Buick. Follow along as we convert a Holley 3310 into a thoroughly modern, 870 cfm high performance fuel delivery system.
Proform Specialty Auto Parts USA, Inc., P.O. Box 306, Roseville, MI 48066, phone (810) 774-2500, fax (810) 778-7775, www.proformparts.com